For certain applications, a back-lit illumination system having a very shallow depth is highly desirable. Such systems are commonly configured with one or more light sources, a waveguide for collecting and distributing the light from the light source, and a collimating apparatus for extracting the light from the waveguide. A significant depth savings can be achieved by coupling the light source through the edge of the waveguide.
The amount of light extracted from the system is proportional to the number of reflections or bounces that occur within the waveguide, the number being inversely proportional to the thickness of the waveguide. To obtain maximum light output, a thin waveguide is preferable. However, this results in edges having a small surface area, limiting the size of the light source that can directly adjoin the edge of the waveguide. On the other hand, if the surface area of the edge is increased, the extraction efficiency of the waveguide will decrease.
It would be highly desirable to utilize a thin waveguide yet provide maximum light source input. Further, a highly reflective and powerful light source would also be desirable.